Studies on the prevention of respiratory distress syndrome of infants due to hyaline membrane disease with plasminogen.

Hyaline membrane disease (HMD) is leading single cause of death of newborn, premature infants. The "hyaline membranes" consist chiefly of fibrin. The clinical manifestation of HMD is the respiratory distress syndrome (RDS). Infants with RDS were treated with urokinase-activated human plasmin in a previous clinical trial. Survival rate was increased in the plasmin treated group as compared to the placebo recipients. However, cost and difficulty in the preparation of the enzyme made this treatment impractical. We, as well as others, have shown the premature infants lack serum plasminogen; thus they are unable to develop effective fibrinolysis and are defenseless against pulmonary fibrin deposition. Therefore, plamsinogen was tested as a possible preventive agent in RDS due to HMD. In a double blind, randomized study, infants between 1 and 2.5 kg birth weight received plasminogen or placebo shortly after birth, and were then followed for development of RDS. After 100 infants were entered into the study, the code was broken and results were evaluated to assure safety of the procedure. Among the 100 infants, 51 received placebo, 49 received plasminogen. Among the infants who received placebo, seven developed mild, and ten developed severe respiratory distress; of these ten, five died with histopathologically documented HMD. Two infants died from causes other than HMD. Among the 49 infants treated with plasminogen, 13 developed mild and three developed severe respiratory distress. There was no death due to HMD. Two deaths were due to other causes. Factors placing the infant at risk from HMD (degree of prematurity, sex, cesarean section, bleeding episodes during pregnancy, maternal diabetes) were found to be evenly distributed between control and treated groups. Since completing the first phase of the study, data of an additional 277 infants has become available. Although the code was not broken in this series, a preliminary look at mortality data in comparison with mortality data of the first series of 100 (in which the code was broken) suggests that preventive activity of plasminogen has been maintained in the second phase of the study.